Automatic control device for the toner concentration within a developer in an electrostatic copy machine

ABSTRACT

In a successive development of the images on an electrostatic copy machine, toner concentration within the developer is continuously detected in an optical manner and the supply of the toner to the developer is automatically controlled in accordance with thusly detected time sequential deviation in the toner concentration so as to compensate for the deviation, thereby the toner concentration can be maintained constant even when the copying operation is repeated many times in succession.

United States Patent 1191 Kishi et a1.

[ AUTOMATIC CONTROL DEVICE FOR THE TONER CONCENTRATION WITHIN ADEVELOPER IN AN ELECTROSTATIC COPY MACHINE [75] Inventors:HirotoshiKishi; Yousuke Igarashi;

Takeo Tano, all of Tokyo, Japan [73] Assignee: Iwatsu Electric Co.,Ltd., Tokyo,

Japan 22 Filed: Aug. 27, 1970 21 App]. No.2 67,369

[30] Foreign Application Priority Data Nov. 15, 1969 Japan ..44/91170Nov. 15, 1969 Japan ..44/9l17l [52] US. Cl. ..95/89 R, 117/37 LE, 118/7,118/637, 137/93, 355/10, 250/218 [51] Int. Cl. ..G03d 3/00 [58] Field ofSearch ..355/l0; 95/89; 118/637, 7, 118/8, 9; 250/218; 117/37 L; 137/91,92, 93

[56] References Cited UNITED STATES PATENTS Jan.23,1973

3,381,662 5/1968 K616 6:61 ..ll8/637 3,369,524 2 1968 Fuhrer ..1 18/6371,794,222 2/1931 Whitney ..137/93 x 3,561,344 2/1971 Frutiger ..95/893,354,802 ll/l967 Doucette et a]. ..355/l0 2,979,066 4/1961 Christie..137/93 x Primary ExaminerSamuel S. Matthews Assistant Examiner-RichardM Sheer AttorneyRobert E. Burns and Emmanuel J. Lobato [57] ABSTRACT Ina successive development of the images on an electrostatic copy machine,toner concentration within the developer is continuously detected in anoptical manner and the supply of the toner to the developer isautomatically controlled in accordance with thusly detected timesequential deviation in the toner concentration so as to compensate forthe deviation, thereby the toner concentration can be maintainedconstant even when the copying operation is repeated many times insuccession.

10 Claims, 13 Drawing Figures 2,535,181 12/1950 Way ..L250 218 X3,368,526 2/1968 Matsumoto et a1 ..l18/423 PMENTEI] JAN 23 I975 SHEET 2OF 4 PAIENTEDJAII 23 I975 SHEET 3 [IF 4 DRIVER CIRCUIT POWER AMPLIFIERAMPLIFIER I2 24 PHOTOELECTRIC CELL PHOTOELECTRIC CELL Fig. 8 4 ;2

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Fig. 85

AUTOMATIC CONTROL DEVICE FOR THE TONER CONCENTRATION WITHIN A DEVELOPERIN AN ELECTROSTATIC COPY MACHINE The present invention relates to anautomatic control device of the toner concentration within a developeron an electrostatic copy machine, more particularly rclates to anautomatic device for controlling the supply rate of the toner to thedeveloper in accordance with the time sequential deviation of therelevant toner concentration within the developer from the presetcommand.

In order to repeat the copying operation many times in succession on awet type electrostatic copy machine with uniform tone of imagesdeveloped on the given photosensitive surfaces, it is necessary that thecontent ratio of the toner within the developer (hereinafter referred toas the toner concentration) should be maintained constant throughout theoperation. Conventionally, this control work was performed throughmanual operation, wherein a certain quantity of toner was supplied tothe developer basing upon the judgement by the operator. Because thiscompensation work was based upon the manual work and the judgement bythe operator, it was actually difficult to maintain the tonerconcentration always exactly constant. Therefore, it was almostimpossible to obtain images of uniformly clear tone on a plurality ofphotosensitive surfaces supplied in succession to the copy machine.Further, it was relatively troublesome work to manually control thequaiitity of the toner to be supplied to the developer throughout thecopying operation, especially when the copying operation has to berepeated many times.

There is another method of maintaining the toner concentration constant,wherein a prescribed quantity of toner is added to the developer atselected cycle or cycles of the copying operation regardless of actualtoner concentration of the relevant developer. This method is alsoaccompanied with drawbacks the same with that above described.

In order to obviate the drawbacks encountered in the manual control ofthe toner concentration within the developer, there is proposed anautomatic method of controlling the supplying rate of toner to thedeveloper through detection of the actual toner concentration in thedeveloper and the detection of the toner concentration is performedthrough a continuous optical measurement of the toner concentration ofdeveloper. Generally in this optical measurement, the developer iscontained within a bath having a transparent window, the window issubjected to a light ofa constant intensity emerging from a givenluminous source and the change in the intensity of the light afterpermeating through the developer is measured, thereby the correspondingtoner concentration within the measured developer being known. In thecase of this method, since the material forming the transparent windowis always in a direct contact with the developer in the bath and iscontaminated considerably during a long time use thereof. Contaminationof the window causes reduction in the intensity of the light permeatedthrough the developer and the detected intensity of the light does notcorrespond to the actual toner concentration within that developer.

One of the solutions to this window contamination trouble is a provisionof a wiper or wipers to the transparent window for the permeation of thelight. In this connection, however, provision of such an additionalmechanical part causes increase in the installation cost of themeasuring arrangement. Further, great difficulty resides in the perfectsealing of the connection between the wiper mechanism and the drivingsource of the mechanism. Removal of the contamination is effective onlywithin the area over which the wiper mechanism operates and a directcontact of the wiper with the window tends to accidentally damage thewindow material.

Another solution to this window contamination trouble is the use ofresonator plate or plates for the part to be kept free fromcontamination. This solution may be substituted by the provision ofsupersonic vibration to the parts to be kept free from contamination. Inthese cases, the vibrating parts must be composed of a light permeablemember such as made of crystal material and provision of suitablemechanism for effectuating such vibration is inevitably required, also,resulting in the complicated construction of the entire arrangement andincrease in the cost thereof.

A principal object of the present invention is to provide an automaticcontrol device of the toner concentration within a developer on anelectrostatic copy machine, thereby the toner concentration within thedeveloper being successfully maintained constant during a long timerepeated copying operation.

Another object of the present invention is to provide a device forperforming the automatic control of the toner concentration of thedeveloper in an exact and stable manner without any time lag and directcontact of the detecting arrangement with the developer.

Still another object of the present invention is to provide a device fordeveloping uniformly clear images on a plurality of photosensitivesurfaces supplied in succession.

In order to attain the above-recited objects, in the device of thepresent invention, a filmy flow of the developer is temporarily formedin the circulation path of the developer through the developer bath andthe image developing part of the copy machine and intensity of the lightpermeating across through the filmy flow is photoelectrically detected,the intensity of the light being dependent upon the toner concentrationof the relevant developer. Supply of the toner to the developer isautomatically controlled in its rate in accordance with the detectedtoner concentration within the developer, thereby time sequentialdeviation of the toner concentration within the developer beingcompensated.

Further features and advantages of the present invention will be moreapparent from the ensuing description, reference being made to theaccompanying drawings, wherein;

FIG. 1 is a partly-sectional side view of an embodiment of the automaticcontrol device of the present invention,

FIG. 2 is a partly-sectional enlarged fragmentary view of the automaticcontrol device shown in FIG. 1,

FIG. 3 is a section taken along the line Ill-III in the device shown inFIG. 2,

FIG. 4 is a plan-sectional view of the toner concentration detectingpart of the device shown in FIG. 2,

FIG. 5 is a diagrammatic representation of the optical detectingmechanism used in the device shown in FIG. 2,

FIG. 6A is a fragmentary perspective view of an embodim ent of the guidefor the filmy flow formation,

FIG. 6B is a fragmentary perspective view of another embodiment of theguide for the filmy flow formation,

FIG. 7 is a diagrammatic representation of the electric circuit used inthe device of the present invention,

FIGS. 8A, 8B and 8C are circuit diagrams of actual examples of theelectric circuit shown in FIG. 7,

FIG. 9 is another example of an embodiment of the automatic controldevice of the present invention,

FIG. 10 is a circuit diagram used in the automatic control device shownin FIG. 9.

Referring to FIG. 1, there is shown an entire arrangement of anembodiment of the automatic control device of the present inventionhlnthe shown arrangement, a developer bath 1 is internally provided with acirculation pump 2 for compulsorily circulating the developer. Beingconnected to this developer bath 1, an image developing part 3 isprovided above the developer bath 1. The developer bath 1 is alsoconnected to a bath toner concentration detector part 4 and a tonersupply mechanism 6 for supplying prescribed amounts of toner from atoner supply source 7 to the developer when required. By the compulsorycirculating effect by the circulation pump 2, the developer within thedeveloper bath 1 is supplied to the image developing part 3, the tonerconcentration detector part 4 and the toner supply mechanism 6.

The detailed arrangement of the toner concentration detector part 4 isshown in FIG. 2, wherein an overflow tank 8 is internally provided witha dam wall 16 dividing the overflow tank 8 into two parts of differentdeveloper levels. The first part of the overflow tank 8 of higherdeveloper level is provided with a developer inlet 14 connected to thetoner supply mechanism 6 whereas the second part of the overflow tank 8of lower developer level is provided with an overflown developer outlet17. A horizontal member is projected from an inside wall of the overflowtank 8 at an upper position facing the developer inlet 14 so thatgushing of liquid from theinlet 14 into the overflow tank 8 is quelled.At the bottom of the first part of the overflow tank 8, which isprovided with a developer outlet 9 which, as seen in FIGS. 2 and 3 is anarrow elongated slit having downwardly converging opposite side walls.The developer flowing through the slit 9 falls downwardly in the form ofa thin unconfinedsheet or film between opposite vertical legs of aU-shaped guide 11 formed integrally with the tank. At a dispositionspacedly sandwiching thusly formed thin developer filmy flow, a lightsource 12 is stationarily located in a face to face relationship to aphotoelectric cell 13 located stationarily, also. At a position asidefrom the developer filmy flow formation, another photoelectric cell 19and a filter 18 are stationarily provided, which filter 18 has a lightpermeability the same with that possessed by a developer of a standardtoner concentration (see FIG. 3). Now, referring back to theillustration shown in FIG. 2 again, the toner supply mechanism 6 isinternally provided with a circulation pipe 22 connected to thedeveloper inlet 14 of the overflow tank 8 and a supply valve 21 forgoverning the supply of the toner from the toner supply source 7 intothe developer flowing through the circulation pipe 22. The supply valve21 is connected to a solenoid 23 controlled by the toner concentrationdetector part 4 via suitable intermediate equipment hereinafterexplained in detail.

In the above-described construction of the automatic control device ofthe present invention, the developer is introduced into the first partof higher developer level of the overflow tank 8 passing through thedeveloper inlet 14 due to the compulsory circulation pump 2 and thuslyintroduced developer falls down through the developer outlet 9 due toits own weight. At this moment, owing to the presence of the guide 11,the developer falls in the form of a thin filmy flow whereas remainderof the developer flowing over the dam wall 16 is discharged out of theoverflow tank 8 through the overflow developer outlet 17. In this filmyflow formation mechanism, the overflow tank 8 functions so as to providethe filmy flow with constantly uniform thickness, thereby the lightpermeability of the developer filmy flow is not affected to anappreciable extent by the time sequential deviation in the thicknessthereof.

The locational relationship between the light source 12, thephotoelectric cell 13, the other photoelectric cell 19, the filter l8and the guide for filmy flow formation 11 will be better understood fromthe illustration shown in FIG. 4, wherein the light emitted form thecommon light source 12 is sensed by both photoelectric cells 13 and 19,the latter being through the filter 18. The difference in theintensities of the light thusly sensed is utilized for detecting thetoner concentration of the corresponding developer.

The above-described optical detecting mechanism of the tonerconcentration within the developer is diagrammatically shown in FIG. 5in a simplified illustravia the filter 18 which,'as mentioned above, hasthe light permeability the same with that possessed by the developer ofthe standard toner concentration. In reference to the difference in theintensities of the light thusly sensed, the opening magnitude of thetoner supply valve 21 (see FIG. 2) is controlled so as to maintain thetoner concentration within the developer constant in an automatic mannervia electric arrangement hereinafter explained.

The guide 11 used for the filmy flow formation can be given in the formof a downwardly U-shaped' wire such as shown in FIG. 6A or a thin platesuch as shown in FIG. 6B. In the case of the latter, the plate isprovided with a suitably dimensioned central aperture for the passing ofthe light emitted from the light source.

A principal arrangement of the electric circuit advantageously usable inthe device of the present invention is shown in FIG. 7, wherein thephotoelectric cells 13 and 19 are connected to a differential amplifiercircuit 31. Only when a difference in the magnitude of the lightreceived is produced between the two photoelectric cells 13 and 19, thedifferential amplifier circuit 31 generates a corresponding outputsignal, which is brought into a driver circuit 33 via a power amplifiercircuit 32. Upon reception of thusly amplified signals,

the driver circuit 33 produces operational signals so as to open thetoner supply valve 21 (see FIG. 2) and the toner is supplied, due to itsown weight, from the toner supply source 7 to the developer within thecirculation pipe 22.

As is self-obvious from the foregoing description, the difference in themagnitude of the light received by the photoelectric cells 13 and 19 iscaused by dilution of the actual toner concentration. So, withadvancement of the new toner supply, the actual toner concentrationgradually approaches the prescribed value. Upon revival of theprescribed toner concentration, an electric balance is established inthe differential amplifier circuit 31 and no further output signalstherefrom is produced. This absence of the output signals leads to thedisappearance of the operational signals from the driver circuit 33 andthe valve 21 is closed accordingly so as to stop the toner supply.

An actual example of the circuits 31, 32 and 33 is shown in FIG. 8A.

In the shown arrangement, the differential circuit includes thephotoelectric cells 13 and 19, an emitter resistor 34, a variableresistor 36 and transistors 37 and 38; the power amplifier circuit 32includes a transistor 39; and the driver circuit 33 includes a relay 41and the solenoid 23. Further, an electric source 42 is provided forexciting a solenoid 23 and biasing purpose to the electric circuit.

Another actual example of the circuits 31, 32 and 33 is shown in FIG.8B. In the shown arrangement, the driver circuit 33 includes thesolenoid 23, a thyrister 43 and an AC electric source 44 for exciting asolenoid 23. Further, an electric source 46 for biasing purpose isprovided also.

In case the toner concentration within the developer is required tochange purposely for any particular reason, for example because of thedifference in the clearness in the originals, the filter 18 should bechanged accordingly. This is one of the very advantageous features ofthe art of the present invention. Only by changing the type or kind ofthe filter 18, the resulting toner concentration can be changed asdesired.

This adjustment can be effected by application of adjustment to thevariable resistor 36 used in the electric circuit also.

Further actual example of the circuits 3], 32 and 33 is shown in FIG.8C. In the shown arrangement, when the toner concentration becomes weak,the light received by the photoelectric cell 13 increases thereby thedifferential amplifier composed of transistors 37 and 38 becomes anunbalanced condition. As a result of this, the relay 51 connected to acollector of the transistor 38 is actuated and then renders the valve ofthe toner supply source 53 open. On the other hand, when the tonerconcentration becomes thick by supplying the toner, the relay 52connected to a collector of the transistor 37 is actuated and then thevalve of the new dispersion liquid 54 opens. As a result of this, theconcentration of the toner becomes a constant value. Further, byshorting the load resistor 55, the toner can be supplied manuallythereby a thicker concentration than the predetermined value can beobtained.

An another embodiment of the control device of the present inventionshown in FIG. 9 is further provided with a float 47 which actuates acommutating switch 48 also shown in FIG. 10. The electrical circuit usedin the embodiment in FIG. 9 is shown in FIG. 10. Referring to FIG 10, acontact 50a is closed by actuating a relay 50 during a constant time,every time a photosensitive paper passes in the electrostatic copymachine. In the case of the control device which is not provided with afloat, when the circulation of the developer is stopped due to thedecreasing of the developer, the passage of the developer for the tonerconcentration detector part 4 decreases, thereby the light permeabilitybecomes increased, that is, the same effect wherein the concentration ofthe toner decreases. Referring to FIG. 9, the same part of FIG. 1 suchas the circulation pump 2, the image developing part 3 etc. are omittedfor the convenience of explanation. The float 47 moves upwardly ordownwardly in accordance with the level of the developer. When the levelof the developer becomes inferior to the nominal level of the developer,a common terminal 48a of the commutation switch 48 is switched to aterminal 480 and the alarm lamp 49 is illuminated. At the same time, thecircuit of the solenoid 23 is opened thereby an unuseful supply of thetoner being prevented. By detecting an insufficiency of the developer bythe illumination of the alarm lamp 49 and supplying a new dispersionliquid, the level of the developer rises. Then, the common terminal 480of the commutation switch 48 returns to a terminal 48b thereby theautomatic control device of the toner concentration being reoperated. Inthe actual case, it is preferable that consideration is taken concerningthe time lag between the illumination of the alarm lamp 49 and thesupply of the dispersion liquid.

While the invention has been described in conjunction with certainembodiments thereof it is to be understood that various modificationsand changes may be without departing from the spirit and scope of theinvention.

What is claimed is:

1. An automatic control device for controlling toner concentration in aliquid developer in an electrostatic copying machine comprising, meansfor supplying toner to such liquid developer, pumping means forcirculating liquid developer along a flow path, a receptacle in saidflow path having a plurality of walls, one of said walls having an inlettherein to receive liquid developer from said pumping means, one of saidwalls of said receptacle having a narrow elongate discharge orificetherein through which a portion of such liquid developer entering saidreceptacle is discharged in a vertically downward direction in the formofa thin free falling sheet along a vertical flow path; overflow meansin said receptacle for discharging excess liquid developer from saidreceptacle and for maintaining a constant pressure head on said orificeand a constant flow rate along said vertical flow path, means in saidvertical flow path for guiding such thin sheet of liquid developer alongsaid vertical flow path in the form of a smooth thin laminar sheetopposite faces of which are unsupported; means for continuouslyoptically detecting the light permability of such thin laminar sheet ofliquid developer and for detecting toner concentration in such liquiddeveloper, and means controlled by said detecting means for controllingthe supply of toner from said toner supply means to such liquiddeveloper in accordance with detected time sequential deviation in tonerconcentration in such liquid developer.

2. An automatic control device as claimed in claim 1, wherein saidoverflow means comprises an'overflow dam dividing said receptacle into afirst portion into which liquid developer flows from said inlet and fromwhich a portion of such liquid developer is discharged through saidorifice and a second portion into which excess liquid developer flowsover said dam and is discharged from said receptacle.

3. An automatic control device as claimed in claim 1, wherein saidorifice comprises a narrow elongate slot in one of said wells of saidreceptacle, said slot having downwardly converging opposite side walls.

4. An automatic control device as claimed in claim 1, wherein saidguiding means comprising a U-shaped wire with parallel legs extendingvertically downwardly respectively at opposite ends of said elongatedischarge orifice.

5. An automatic control device as claimed in claim 1, wherein saidguiding means comprises a thin plate extending vertically down from saidelongate discharge orifice and having an aperture for passage of lightfor operation of said optical detecting means.

6. An automatic control device as claimed in claim 1, wherein saidoptical detecting means comprises a light source and a photoelectriccell so disposed respectively on opposite sides of such thin sheet ofliquid developer that light from such source passes only through saidsheet in travelling from said source to said photoelectric cell.

7. An automatic control device as claimed in claim 6,

wherein said optical detecting means further comprises a secondphotoelectric cell positioned to receive light from said light source, afilter of selected density between said second cell and said lightsource and electric circuit means for comparing signals received fromsaid photoelectric cells.

8. An automatic control device as claimed in claim 7, wherein saidcircuit means comprises a differential amplifier circuit havingtwoinputs and an output, means connecting said inputs respectively tosaid photoelectric cells, a power amplifier connected to the output ofsaid differential amplifier circuit, and a driven circuit connected tosaid power amplifier circuit.

9. An automatic control device as claimed in claim 1, wherein said meansfor controlling the supply of toner comprises a second flow path forsuch liquid developer from said pumping means, a toner supply passagefrom said toner supply means to said second flow path, a solenoid valvecontrolling flow of toner through said passage and an electric circuitfor actuating said solenoid valve in response to signals from saidoptical de-' tecting means.

10. An automatic control device as claimed in claim 1 further comprisinga float detecting the liquid level of liquid developer, an alarm, andcircuit means comprising commutating switching means actuated by saidfloat to deactivate said toner supply control means to prevent deliveryof toner from such toner supply means to said liquid developer and toactivate said alarm when the level of liquid developer falls below apredetermined level.

* II! v

1. An automatic control device for controlling toner concentration in aliquid developer in an electrostatic copying machine comprising, meansfor supplying toner to such liquid developer, pumping means forcirculating liquid developer along a flow path, a receptacle in saidflow path having a plurality of walls, one of said walls having an inlettherein to receive liquid developer from said pumping means, one of saidwalls of said receptacle having a narrow elongate discharge orificetherein through which a portion of such liquid developer entering saidreceptacle is discharged in a vertically downward direction in the formof a thin free falling sheet along a vertical flow path; overflow meansin said receptacle for discharging excess liquid developer from saidreceptacle and for maintaining a constant pressure head on said orificeand a constant flow rate along said vertical flow path, means in saidvertical flow path for guiding such thin sheet of liquid developer alongsaid vertical flow path in the form of a smooth thin laminar sheetopposite faces of which are unsupported; means for continuouslyoptically detecting the light permability of such thin laminar sheet ofliquid developer and for detecting toner concentration in such liquiddeveloper, and means controlled by said detecting means for controllingthe supply of toner from said toner supply means to such liquiddeveloper in accordance with detected time sequential deviation in tonerconcentration in such liquid developer.
 2. An automatic control deviceas claimed in claim 1, wherein said overflow means comprises an overflowdam dividing said receptacle into a first portion into which liquiddeveloper flows from said inlet and from which a portion of such liquiddeveloper is discharged through said orifice and a second portion intowhich excess liquid developer flows over said dam and is discharged fromsaid receptacle.
 3. An automatic control device as claimed in claim 1,wherein said orifice comprises a narrow elongate slot in one of saidwells of said receptacle, said slot having downwardly convergingopposite side walls.
 4. An automatic control device as claimed in claim1, wherein said guiding means comprising a U-shaped wire with parallellegs extending vertically downwardly respectively at opposite ends ofsaid elongate discharge orifice.
 5. An automatic control device asclaimed in claim 1, wherein said guiding means comprises a thin plateextending vertically down from said elongate discharge orifice andhaving an aperture for passage of light for operation of said opticaldetecting means.
 6. An automatic control device as claimed in claim 1,wherein said optical detecting means comprises a light source and aphotoelectric cell so disposed respectively on opposite sides of suchthin sheet of liquid developer that light from such source passes onlythrough said sheet in travelling from said source to said photoelectriccell.
 7. An automatic control device as claimed in claim 6, wherein saidoptical detecting means further comprises a second photoelectric cellpositioned to receive light from said light source, a filter of selecteddensity between said second cell and said light source and electriccircuit means for comparing signals received from said photoelectriccells.
 8. An automatic control device as claimed in claim 7, whereinsaid circuit means comprises a differential amplifier circuit having twoinputs and an output, means connecting said inputs respectively to saidphotoelectric cells, a power amplifier connected to the output of saiddifferential amplifier circuit, and a driven circuit connected to saidpower amplifier circuit.
 9. An automatic control device as claimed inclaim 1, wherein said means for controlling the supply of tonercomprises a second flow path for such liquiD developer from said pumpingmeans, a toner supply passage from said toner supply means to saidsecond flow path, a solenoid valve controlling flow of toner throughsaid passage and an electric circuit for actuating said solenoid valvein response to signals from said optical detecting means.
 10. Anautomatic control device as claimed in claim 1 further comprising afloat detecting the liquid level of liquid developer, an alarm, andcircuit means comprising commutating switching means actuated by saidfloat to deactivate said toner supply control means to prevent deliveryof toner from such toner supply means to said liquid developer and toactivate said alarm when the level of liquid developer falls below apredetermined level.